text: Due to the decreased nucleophilicity of Grignard reagents (organomagnesium) and organozinc reagents, non-catalyzed carbomagnesiation and carbozincation reactions are typically only observed on activated or strained alkenes and alkynes. For example, electron withdrawing groups like esters, nitriles or sulfones must be in conjugation with the carbon-carbon π-system (see Michael reaction) or a directing group like an alcohol or amine must be nearby to direct the reaction. These reactions can be catalyzed by a variety of transition metals such as iron, copper, zirconium, nickel, cobalt and others.
  Illustrative is the Fe-catalyzed reaction of methylphenylacetylene with phenylmagnesium bromide, which generates a vinyl magnesium intermediate.  Hydrolysis affords the diphenylalkene: